Portable media devices have become an extremely common way for playback of media. Devices that playback digitally stored audio, such as iPods® and mobile phones are used for the playback of both music and audiovisual content. An increasing trend for such devices is their attachment to a wide variety of reproduction devices and systems for playback of the audio. For example, a user might attach her iPod to a home theater system that include speakers, to a TV with speakers, or to a standalone docking station with speakers. Each of these is an example of a different playback system to which the same portable device might be attached.
Even though portable playback devices for digitally stored audio have been available for more than a decade, and portable devices for playback of digitally stored audio on disk or tape have been around for decades, there still is a need for equalization of playback of audio from such devices when connected to one of a set of possible playback systems. As examples of how long such devices have been commercially available, the RIO® portable playback device by Diamond Multimedia, of California, was introduced in 1998 for MP3 playback. The PJB-100 Personal Jukebox by HanGo Electronics Co., Ltd. of South Korea is generally acknowledged to be the first hard-drive based device and was commercially introduced in 1999. The Apple IPOD was introduced in 2001. Each of these devices included a digital processor in order to decompress and render the digitally stored compressed audio.
It would be advantageous to include in a portable media device equalization filters to be applied to audio signals directly in the portable media device to equalize for the overall system comprising the portable media device and the playback system to which it is attached for an improved listening experience. It further would be advantageous to include in the portable media device sets of equalization filters, each set applicable to a different ones of the playback systems to which the portable device might be attached to equalize for the overall system comprising the portable media device and the playback system to which it is attached. It also would be advantageous to have an end-user operated method of determining, using a portable media device, a set of equalization filters to use in the portable media device with a particular playback system to equalize for the overall system comprising the portable media device and the playback system to which it is attached.